Pressure-induced phase transitions for goethite investigated by Raman spectroscopy and electrical conductivity

ABSTRACT

We reported two pressure-induced phase transitions of goethite up to ∼35 GPa using a diamond anvil cell in conjunction with ac impendence spectroscopy, Raman spectra at room temperature. The first pressure-induced phase transition at ∼7.0 GPa is manifested in noticeable changes in six Raman-active modes, two obvious splitting phenomena for the modes and the variations in the slope of conductivity. The second phase transition at ∼20 GPa was characterized by an obviously drop in electrical conductivity and the noticeable changes in the Raman-active modes. The variations in activation energy with increasing pressure were also discussed to reveal the electrical properties of goethite at high pressure.

KEYWORDS:

• Goethite
• high pressure
• Raman spectroscopy
• electrical conductivity
• phase transition

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This research was financially supported by the Strategic Priority Research Program (B) of the Chinese Academy of Sciences [grant number XDB 18010401], Key Research Program of Frontier Sciences of CAS [grant number QYZDB-SSW-DQC009], ‘135' Program of the Institute of Geochemistry of CAS, Hundred Talents Program of CAS and National Science Foundation of China of China [grant numbers 41474078, 41774099 and 41772042].